Pension Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 Years	Dec. 31, 2010	Dec. 31, 2009
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Gains (Losses), before Tax	$ 8,501,000	$ (5,892,000)
Defined Benefit Plan, Benefits Paid, Qualified Pension Plan	(1,476,000)	(1,675,000)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation Beginning of Year	23,867,000	18,550,000
Defined Benefit Plan, Service Cost	3,800,000	3,392,000	2,500,000
Defined Benefit Plan, Interest Cost	1,184,000	1,120,000	934,000
Defined Benefit Plan, Amendments	170,000	0
Defined Benefit Plan, Actuarial Loss	1,957,000	2,480,000
Defined Benefit Plan, Benefits Paid	(1,498,000)	(1,675,000)	(945,000)
Defined Benefit Plan, Benefit Obligation End of Year	29,480,000	23,867,000	18,550,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	10,332,000	9,101,000
Defined Benefit Plan, Actual Return on Plan Assets	(176,000)	1,181,000
Defined Benefit Plan, Employer Contribution	5,260,000	1,725,000	2,000,000
Defined Benefit Plan, Benefits Paid	(1,498,000)	(1,675,000)	(945,000)
Defined Benefit Plan, Fair Value of Plan Assets End of Year	13,940,000	10,332,000	9,101,000
Defined Benefit Plan, Funded Status of Plan	(15,540,000)	(13,535,000)
Defined Benefit Plan, Accumulated Benefit Obligation	21,697,000	17,457,000
Defined Benefit Plan, Accumulated Unfunded Benefit Obligation	7,757,000	7,125,000
Pre-tax Amounts Recognized in Accumulated Other Comprehensive Income
Defined Benefit Plan, Amounts Recognized In Other Comprehensive Income, Actuarial Losses, Before Tax	(3,014,000)	(1,937,000)	(239,000)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	170,000	0
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Transition Assets (Obligations), before Tax	0	0
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	8,671,000	(5,892,000)
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year	586,000
Total Other Comprehensive Income (Loss)		(1,570,000)	119,000
Components of Net Periodic Benefit Costs for Both Pension Plans
Defined Benefit Plan, Expected Return on Plan Assets	(880,000)	(638,000)	(430,000)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(170,000)	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	0
Defined Benefit Plan, Amortization of Gains (Losses)	405,000	367,000	372,000
Defined Benefit Plan, Net Periodic Benefit Cost	4,509,000	4,241,000	3,376,000
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net (Gain) Loss Recognized in Net Periodic Benefit Cost, Net of Tax	(405,000)	(367,000)	(358,000)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.70%	5.30%	6.10%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	6.20%	6.20%	6.20%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.30%	6.10%	6.10%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	7.50%	7.50%	7.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	6.20%	6.20%	6.20%
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	4,900,000
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	60.00%
Defined Benefit Plan, Equity Securities	61.80%	60.80%
Defined Benefit Plan, Target Allocation Percentage of Assets, Debt Securities	40.00%
Defined Benefit Plan, Debt Securities	37.70%	39.20%
Defined Benefit Plan, Target Allocation Percentage of Assets, Other	0.00%
Defined Benefit Plan, Other Plan Assets	0.50%	0.00%
Defined Benefit Plan, Total Target Asset Allocation	100.00%
Defined Benefit Plan, Total Asset Allocation	100.00%	100.00%
Future Benefit Payments
Defined Benefit Plan, Expected Future Benefit Payments in Year One	1,296,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	2,360,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	2,513,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	2,205,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	2,668,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 23,258,000
Defined Benefit Plan, Percent Vested After Two Years of Service	40.00%
Defined Benefit Plan, Years of Service Required for Initial Vesting	2
Defined Benefit Plan, Annual Vesting Increment	20.00%